Harvard University

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Dynamic Voltage and Frequency Scaling (DVFS) is an effective technique for controlling microprocessor energy and performance. Existing DVFS techniques are primarily based on hardware, OS time-interrupts, or static-compiler techniques. However, substantially greater gains can be realized when control opportunities are also explored in a dynamic compilation environment. There are several...

Simultaneous Multi-Threading (SMT) and Chip Multi-Processing (CMP) both allow a chip to achieve greater throughput, but their relative energy-efficiency and thermal properties are still poorly understood. In this paper, the authors use Turandot, PowerTimer, and HotSpot to explore this design space for a POWER4/POWER5-like core. For an equal-area comparison with...

The authors present a new operating system scheduling algorithm for multicore processors. Their algorithm reduces the effects of unequal CPU cache sharing that occur on these processors and cause unfair CPU sharing, priority inversion, and inadequate CPU accounting. They describe the implementation of their algorithm in the Solaris operating system...

The authors investigated how operating system design should be adapted for Multi-Threaded (MT) Chip Multi-Processors (CMP) - a new generation of processors that exploit thread-level parallelism to mask the memory latency in modern workloads. They determined that the L2 cache is a critical shared resource on CMT and that an...

The authors present a new, more constructive proof of von neumann's min-max theorem for two-player zero-sum game - specifically, an algorithm that builds a near-optimal mixed strategy for the second player from several best-responses of the second player to mixed strategies of the first player. The algorithm extends previous paper...

As the traditional performance gains of technology scaling diminish, one of the most promising directions is building special purpose fixed function hardware blocks, commonly referred to as accelerators. Accelerators have become prevalent in industrial SoC designs for their low power, high performance potential. In this paper, the authors explore thousands...

Current processors increasingly exploit Thread-Level Parallelism (TLP) to improve performance. As a result, multi-core/multi-thread processors are becoming the dominant architectures for domains ranging from mobile platforms to high-performance computing. As technology scales, the number of transistors available will continue to grow every generation. To make full use of those transistors...

Lowering the supply voltage to improve energy efficiency leads to higher load current and elevated supply sensitivity. In this paper, the authors provide the first quantitative analysis of voltage noise in multi-core near-threshold processors in a future 10nm technology across SPEC CPU2006 benchmarks. Their results reveal larger guardband requirement and...

Given the sensitivity of the potential WSN applications and because of resource limitations, key management emerges as a challenging issue for WSNs. One of the main concerns when designing a key management scheme is the network scalability. Indeed, the protocol should support a large number of nodes to enable a...

In this paper, the authors characterize the impact of compiler optimizations on voltage noise. While intuition may suggest that the better processor utilization ensured by optimizing compilers results in a small amount of voltage variation, their measurements on a Intel R Core Duo processor show the opposite - the majority...

Specialized architectures will become increasingly important as the computing industry demands more energy-efficient designs. The application-centric design style for these architectures is heavily dependent on workload characterization of intrinsic program characteristics, but at the same time these architectures are likely to be decoupled from legacy ISAs. In this paper, the...

The authors propose a spectrum analyzer that leverages many networked commodity sensor nodes, each of which samples its portion in a wideband spectrum. The sensors operate in parallel and transmit their measurements over a wireless network without performing any significant computations such as FFT. The measurements are forwarded to the...

Sensor networks are an exCltmg new kmd of computer system. Consisting of a large number of tiny, cheap computational devices physically distributed in an environment, they gather and process data about the environment in real time. One of the central questions in sensor networks is what to do with the...

The authors present Compressed Statistical Testing (CST) with an illustrative application to radar target detection. They characterize an optimality condition for a compressed domain test to yield the same result as the corresponding test in the uncompressed domain. They demonstrate by simulation that under high SNR, a likelihood ratio test...

The process of detecting logical faults in Integrated Circuits (ICs) due to manufacturing variations is bottlenecked by the I/O cost of scanning in test vectors and offloading test results. Traditionally, the output bottleneck is alleviated by reducing the number of bits in output responses using XOR networks, or computing signatures...

The authors are interested in estimating the angle of arrival of an RF signal by using Commercial-Off-The-Shelf (COTS) Software-Defined Radios (SDRs). The proposed COTS-based approach has the advantages of flexibility, low cost and ease of deployment, but - unlike traditional phased antenna arrays in which elements are already phase-aligned -...

The authors describe a method of integrating Karhunen-Loeve Transform (KLT) into compressive sensing, which can as a result improve the compression ratio without affecting the accuracy of decoding. They present two complementary results: by using KLT to find an optimal basis for decoding they can drastically reduce the number of...

The authors propose a Medium Access Control (MAC) protocol for wireless Local Area Networks (LANs) that leverages the theory of compressive sensing. The proposed Compressive Sensing MAC (CS-MAC) exploits the sparse property that, at a given time, only a few hosts are expected to request for radio channel access. Under...

The authors present a chip architecture for a compressive sensing based method that can be used in conjunction with the JTAG standard to detect IC Trojans. The proposed architecture compresses chip output resulting from a large number of test vectors applied to a Circuit Under Test (CUT). They describe their...

The authors create a formal framework for the design of informative securities in prediction markets. These securities allow a market organizer to infer the likelihood of events of interest as well as if he knew all of the traders' private signals. They consider the design of markets that are always...

As the cloud computing paradigm has gained prominence, the need for verifiable computation has grown increasingly urgent. Protocols for verifiable computation enable a weak client to outsource difficult computations to a powerful, but untrusted server, in a way that provides the client with a guarantee that the server performed the...

Computing hardware has been shifting to a multicore paradigm. One extreme of that approach is many-core computing, where a large number of simple processor cores execute in throughput mode. However, this paradigm is not ubiquitous and latency-bound applications do have a place in the workloads of the future. The authors...

Conjugate gradient is an important iterative method used for solving least squares problems. It is compute-bound and generally involves only simple matrix computations. One would expect that the authors could fully parallelize such computation on the GPU architecture with multiple Stream Multiprocessors (SMs), each consisting of many SIMD processing units....

In systems that handle confidential information, the security policy to enforce on information frequently changes: new users join the system, old users leave, and sensitivity of data changes over time. It is challenging, yet important, to specify what it means for such systems to be secure, and to gain assurance...

MonetDB is a state-of-the-art open-source column-store database management system targeting applications in need for analytics over large collections of data. MonetDB is actively used nowadays in health care, in telecommunications as well as in scientific databases and in data management research, accumulating on average more than 10,000 downloads on a...

The results of the authors' experiments using ASIM indicate that when filtering wicked traffic, the best targets for intervention are a small group of the largest ASes. Specifically, they find that intervention by the top 0.2% of ASes (in terms of size) is more effective than intervention by a randomly...

Incorporating wireless transceivers with numerous antennas (such as Massive-MIMO) is a prospective way to increase the link capacity or enhance the energy efficiency of future communication systems. However, the benefits of such approach can be realized only when proper channel information is available at the transmitter. Since the amount of...

Information-theoretic throughput scaling laws are analyzed in an underwater acoustic network with n regularly located nodes on a unit square, in which both bandwidth and received signal power can be severely limited. A narrow-band model is assumed where the carrier frequency is allowed to scale as a function of n....

Many data structures support dictionaries, also known as maps or associative arrays, which store and manage a set of key-value pairs. A multimap is generalization that allows multiple values to be associated with the same key. For example, the inverted file data structure that is used prevalently in the infrastructure...

Spectrum sensing is of fundamental importance to many wireless applications including cognitive radio channel assignment and radiolocation. However, conventional spectrum sensing can be prohibitively expensive in computation and network bandwidth when the bands under scanning are wide and highly contested. In this paper, the authors propose distributed spectrum sensing with...

Compressive sensing has emerged as an important new technique in signal acquisition due to the surprising property that a sparse signal can be captured from measurements obtained at a sub-Nyquist rate. The decoding cost of compressive sensing, however, grows superlinearly with the problem size. In distributed sensor systems, the aggregate...

Compressive sensing has gained momentum in recent years as an exciting new theory in signal processing with several useful applications. It states that signals known to have a sparse representation may be encoded and later reconstructed using a small number of measurements, approximately proportional to the signal's sparsity rather than...

Detecting Trojans in an Integrated Circuit (IC) is an important but hard problem. A Trojan is malicious hardware - it can be extremely small in size and dormant until triggered by some unknown circuit state. To allow wake-up, a Trojan could draw a minimal amount of power, for example, to...

While there has been a great deal of research on provenance systems, there has been little discussion about challenges that arise when making different provenance systems interoperate. In fact, most of the literature focuses on provenance systems in isolation and does not discuss interoperability - what it means, its requirements,...

The Provenance Aware Storage Systems project (PASS) currently collects system-level provenance by intercepting system calls in the Linux kernel and storing the provenance in a stackable filesystem. While this approach is reasonably efficient, it suffers from two significant drawbacks: each new revision of the kernel requires reintegration of PASS changes,...

The authors introduce a joint decoding method for compressive sensing that can simultaneously exploit sparsity of individual components of a composite signal. Their method can significantly reduce the total number of variables decoded jointly by separating variables of large magnitudes in one domain and using only these variables to represent...

Provenance systems can produce enormous provenance graphs that can be used for a variety of tasks from determining the inputs to a particular process to debugging entire workflow executions or tracking difficult-to-find dependencies. Visualization can be a useful tool to support such tasks, but graphs of such scale (thousands to...

Wireless data transfer under high mobility, as found in Unmanned Aerial Vehicle (UAV) applications, is a challenge due to varying channel quality and extended link outages. The authors present FlowCode, an easily deployable link-layer solution utilizing multiple transmitters and receivers for the purpose of supporting existing transport protocols such as...

The 1911 Standard Oil case, everyone knows, was all about price discrimination, "Predatory" pricing, acquisitions under duress, and the like. But there was also a technological element. Defending against monopolization charges, Standard Oil claimed that it had innovated both technologically and in the scale economies-enhancing investments by which it aggressively...

Following Gennaro, Gentry, and Parno (Cryptology ePrint Archive 2009/547), the authors use fully homomorphic encryption to design improved schemes for delegating computation. In such schemes, a delegator outsources the computation of a function F on many, dynamically chosen inputs xi to a worker in such a way that it is...

According to current UN projections, the population of the world age 60 or older will be 2 billion by 2050. With populations aging in nearly all countries, there has been widespread concern about the possible effects on economic growth and on the ability of countries to provide support for their...

The recent financial crisis has led many to question how well businesses deliver consumer financial services and how well regulatory institutions address problems in consumer financial markets. In response, the Obama administration proposed a new agency to oversee consumer financial services, and the recently enacted Dodd-Frank Wall Street Reform and...

In recent years a number of research efforts have focused on effective use of P2P-based systems in providing large scale video streaming services. In particular, live streaming and Video-on-Demand (VoD) systems have attracted much interest. While previous efforts mainly focused on the common challenges faced by both types of applications,...

Monitoring network traffic and classifying applications are essential functions for network administrators. Current traffic classification methods can be grouped in three categories: flow-based (e.g., packet sizing/timing features), payload-based, and host-based. Methods from all three categories have limitations, especially when it comes to detecting new applications, and classifying traffic at the...

High-performance computing has recently seen a surge of interest in heterogeneous systems, with an emphasis on modern Graphics Processing Units (GPUs). These devices offer tremendous potential for performance and efficiency in important large-scale applications of computational science. However, exploiting this potential can be challenging, as one must adapt to the...

Countries differ markedly in the diversification of their exports. Products differ in the number of countries that export them, which the authors define as their ubiquity. They document a new stylized fact in the global pattern of exports: there is a systematic relationship between the diversification of a country's exports...

Path integral techniques for the pricing of financial options are mostly based on models that can be recast in terms of a Fokker-Planck differential equation and that, consequently, neglect jumps and only describe drift and diffusion. The authors present a method to adapt formulas for both the path-integral propagators and...

Globalization has created an international financial network of countries linked by trade in goods and assets. These linkages allow for more efficient resource allocation across borders, but also create potentially hazardous financial interdependence, such as the great financial distress caused by the 2010 threat of Greece's default or the 2008...

The authors analyze an OLG economy with financial frictions and accumulation of both physical and intangible capital. The key difference between these two types of capital is that intangible capital cannot be used as collateral for borrowing. As intangibles become more important relative to physical capital in production, interest rates...

The most widely used economic models of social preferences are specified only for certain outcomes. There are two obvious methods of extending them to lotteries. If we do so by expected utility theory, so that the independence axiom is satisfied, the results imply that the resulting preferences do not exhibit...

This paper develops a dual-self model that is compatible with modern dynamic macroeconomic theory and evidence, and shows how it leads to a wide range of behavioral anomalies concerning risk, including the Allais paradox. The authors calibrate the model to obtain a quantitative fit, by extending the simpler "Nightclub" model...

Driven by the confluence between the need to collect data about people's physical, physiological, psychological, cognitive, and behavioral processes in spaces ranging from personal to urban and the recent availability of the technologies that enable this data collection, wireless sensor networks for healthcare have emerged in the recent years. In...

Economics puts the challenges facing cybersecurity into perspective better than a purely technical approach does. Systems often fail because the organizations that defend them do not bear the full costs of failure. For instance, companies operating critical infrastructures have integrated control systems with the Internet to reduce near-term, measurable costs...

A key way in which banks mitigate the effects of phishing is to remove fraudulent websites or suspend abusive domain names. This 'take-down' is often subcontracted to specialist firms. Prior work has shown that these take-down companies refuse to share 'Feeds' of phishing website URLs with each other, and consequently,...

The authors devise a model for security investment that reflects dynamic interaction between a defender, who faces uncertainty, and an attacker, who repeatedly targets the weakest link. Using the model, the authors derive and compare optimal security investment over multiple periods, exploring the delicate balance between proactive and reactive security...

Embedded systems provide a combination of opportunities and challenges in application and system configuration and management. As an embedded system is most often dedicated to a single application or small set of cooperating tasks, the operating conditions of the system are typically better understood than those of general-purpose computing environments....

This paper makes the case that operating system designs for sensor networks should focus on the coordination of resource management decisions across the network, rather than merely on individual nodes. The authors motivate this view by describing the challenges inherent to achieving a globally efficient use of sensor network resources,...

Supply voltage fluctuations that result from inductive noise are increasingly troublesome in modern microprocessors. A voltage "Emergency", i.e., a swing beyond tolerable operating margins, jeopardizes the safe and correct operation of the processor. Techniques aimed at reducing power consumption, e.g., by clock gating or by reducing nominal supply voltage, exacerbate...

The authors construct the topology of business networks across the population of firms in an emerging economy, Pakistan, and estimate the value that membership in large yet diffuse networks brings in terms of access to bank credit and improving financial viability. They link two firms if they have a common...

American fiscal policy has been procyclical: Washington wasted the expansion period 2001-2007 by running budget deficits, but by 2011 had come to feel constrained by inherited debt to withdraw fiscal stimulus. Chile has achieved countercyclical fiscal policy - saving in booms and easing in recession - during the same decade...

Development involves change. But many development initiatives produce unimpressive levels of change in targeted countries, organizations and outcomes. This is the case in social sector initiatives, core public management reforms, and even macroeconomic adjustment operations. Change is often limited even when countries adopt proposed solutions in their proposed forms, in...

Many reform results fall below expectations in the development arena, especially in the public sector. Do the reforms just need more time to work better, or should the authors adjust the expectations? In addressing this question, the current paper draws from isomorphism to think about potential limits to reform in...

This paper asks how strong African Public Financial Management (PFM) has become, after a decade and more of reform. How well do African PFM systems in place now facilitate effective public financial management? Where are the next challenges and how can they be met? It analyzes recent PFM assessments in...

Fiscal and monetary policy each has a role to play in mitigating the volatility that stems from the large trade shocks hitting commodity-exporting countries. All too often macroeconomic policy is procyclical that is, destabilizing, rather than countercyclical. This paper suggests two institutional innovations designed to achieve greater counter cyclicality, one...

When corporate payout is taxed, internal equity is cheaper than external equity. If there are no perfect substitutes for equity finance, payout taxes may therefore have an effect on the investment of firms. High taxes will favor investment by firms who can finance internally. Using an international panel with many...

This paper studies optimal government debt maturity in a model where investors derive monetary services from holding riskless short-term securities. In a simple setting where the government is the only issuer of such riskless paper, it trades off the monetary premium associated with short-term debt against the refinancing risk implied...

The authors develop an integrated theory of the social identity mechanisms linking workgroup sex and race composition across levels with individual turnover. Analyzing longitudinal human resource data on professionals employed in a large up-or-out knowledge organization, they assess the distinct effects of demographic match with superiors and demographic match with...

In this paper the authors investigate whether greater product market competition increases decentralization. To tackle the issues they collected detailed information on the internal organization of firms across nations. The few datasets that exist are either from a single industry or (at best) across many firms in a single country....

The authors study the framing effects of communication in multiparty bargaining. Communication has been shown to be more truthful and revealing than predicted in equilibrium. Because talk is preference revealing, it may effectively frame bargaining around logic of fairness or competition, moving parties on a path toward or away from...

For the better part of the past decade, the world economy has been dominated by a world economic order that combined Chinese export-led development with US overconsumption. First, the scale of Chinese currency intervention was without precedent, as were the resulting distortions of the world economy. Second, the Chinese have...

The authors have contributed an interesting paper on the comparative benefit of moral rules versus cost-benefit analysis. Many of their specific comments are accurate, useful, and insightful. At the same time, they believe they have misrepresented cost-benefit analysis and have reached a set of conclusions that are misguided and, if...

Policies that would create net benefits for society but would also involve costs frequently lack the necessary support to be enacted because losses loom larger than gains psychologically. To reduce the harmful consequence of loss aversion, the authors propose a new type of policy bundling technique in which related bills...

The standard Utilitarian framework for tax analysis answers this question in the affirmative. This paper can be interpreted in one of two ways. One interpretation is that personal attributes correlated with wages should be considered more widely for determining taxes. Alternatively, if policies such as a height tax are rejected,...

It is often difficult for donors to predict the value of charitable giving because they know little about the persons who receive their help. This concern is particularly acute when making contributions to organizations that serve heterogeneous populations. While the authors have considerable evidence that donors are more generous if...

The advent of file-sharing technology has allowed consumers to copy music, books, video games and other protected works on an unprecedented scale at minimal cost. In this paper, the authors ask whether the new technology has undermined the incentives of authors and entertainment companies to create market and distribute new...

The long-standing argument that focused operations outperform others stands in contrast to theory and evidence supporting a broader scope for organizations. The literature on related diversification at the level of the firm provides some reconciliation of these conflicting observations by suggesting that multi-unit firms with a portfolio of related businesses...

Large organizations often earmark training expenditures for a particular type of service, such as individual coaching, group classes, or consulting work. When a coach or consultant encourages a more systemic solution that could yield a higher return on investment, management often responds, "I have money available only for training." Champions...

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